In cloud computing, data is often distributed to a system of multiple computers connected by one or more communications networks. The system can persist data by storing the data, or different versions of the data, on nonvolatile memory devices, e.g., flash memory or disk memory devices, associated with one or more of the multiple computers. Garbage data can accumulate in the system as files stored by the system are updated such that previous versions of the files store outdated information or redundant occurrences of information.